Melbourne coach Paul Roos has expressed frustration over AFL rule changes.

The league asked umpiring department members Luke Ball and Hayden Kennedy to contact all 18 clubs this week in an effort to clarify the rushed behind rule.

The contentious law has been in the headlines this week after North Melbourne veteran Michael Firrito was pinged in round 17, costing his side a goal.

Roos joined a chorus of confusion on Thursday, questioning the need for recent rule changes and saying he felt for whistle-blowers.

“Because they’re the ones who cop the brunt and it’s not their fault. They’re not the ones who create the rule changes,” Roos said.

“It’s really frustrating.

“When they bring these rules in, they’re un-umpirable.

“If you continually bring in rule changes it’s very, very difficult to keep umpiring to the letter of the law.”

Roos noted he was still confused about what constitutes a deliberately rushed behind.

“Probably like 99.99 per cent (of people),” he added.

“I thought the response from the AFL (to the Firrito call) would be ‘look we can understand why the umpire has made the decision, but it was the wrong decision’.

“When you hear (umpires boss) Hayden come out and justify it, that’s when we all get confused.

“I hadn’t heard about distance from goal. I hadn’t heard about height over the goal umpire’s head. It adds to the confusion.”

Roos also highlighted a controversial 50m penalty awarded in last week’s clash between Sydney and Hawthorn.

Kennedy and AFL chief executive Gillon McLachlan both felt Kieren Jack was rightly penalised but Michael Christian, who is on the AFL’s laws committee, disagreed.

“I was as perplexed by the Kieren Jack 50m penalty as I was (the rushed-behind incident),” Roos said.

“I don’t know whether Kieren is supposed to jump down a manhole?

“I didn’t know he actually had to go sideways, I thought you could actually run through.”